Testing of full face snorkel masks to examine recreational snorkeler deaths.

A recent rise in snorkeling-related deaths in Hawaii has inspired several bans on full face snorkel masks (FFSMs). However, while there are theories to explain the deaths, little physiological data exists about the way the FFSMs provide gas to an exercising subject. To evaluate the safety of the FFSM concept, this study was designed to test how use of a full face snorkel mask (FFSM) may be physiologically different than use of a conventional snorkel, and to assess if any of those differences could lead to increased risk for the snorkeler. Ten (10) volunteer human subjects were tested using a variety of commercially available FFSMs, with real-time monitoring of blood oxygen saturation (SpO2), inspired airway pressure, and inspired and expired levels of carbon dioxide and oxygen. Two of the three FFSM design types were shown not to function as advertised, but none of the masks provided physiologically problematic gas supplies to the snorkelers. While this testing yielded no conclusive "smoking gun" to explain the snorkeler deaths, some of the mask models showed patterns of increasing breathing resistance with water intrusion because of a shared design characteristic, and this increased resistance could potentially create elevated levels of respiratory distress to snorkelers during real-world use.